2ozl

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 2ozl, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Human pyruvate dehydrogenase S264E variant

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

At the junction of glycolysis and the Krebs cycle in cellular metabolism, the pyruvate dehydrogenase multienzyme complex (PDHc) catalyzes the, oxidative decarboxylation of pyruvate to acetyl-CoA. In mammals, PDHc is, tightly regulated by phosphorylation-dephosphorylation of three serine, residues in the thiamin-dependent pyruvate dehydrogenase (E1) component., In vivo, inactivation of human PDHc correlates mostly with phosphorylation, of serine 264, which is located at the entrance of the substrate channel, leading to the active site of E1. Despite intense investigations, the, molecular mechanism of this inactivation has remained enigmatic. Here, a, detailed analysis of microscopic steps of catalysis in human wild-type, PDHc-E1 and pseudophosphorylation variant Ser264Glu elucidates how, phosphorylation of Ser264 affects catalysis. Whereas the intrinsic, reactivity of the active site in catalysis of pyruvate decarboxylation, remains nearly unaltered, the preceding binding of substrate to the, enzyme's active site via the substrate channel and the subsequent, reductive acetylation of the E2 component are severely slowed in the, phosphorylation variant. The structure of pseudophosphorylation variant, Ser264Glu determined by X-ray crystallography reveals no differences in, the three-dimensional architecture of the phosphorylation loop or of the, active site, when compared to those of the wild-type enzyme. However, the, channel leading to the active site is partially obstructed by the side, chain of residue 264 in the variant. By analogy, a similar obstruction of, the substrate channel can be anticipated to result from a phosphorylation, of Ser264. The kinetic and thermodynamic results in conjunction with the, structure of Ser264Glu suggest that phosphorylation blocks access to the, active site by imposing a steric and electrostatic barrier for substrate, binding and active site coupling with the E2 component. As a Ser264Gln, variant, which carries no charge at position 264, is also selectively, deficient in pyruvate binding and reductive acetylation of E2, we conclude, that mostly steric effects account for inhibition of PDHc by, phosphorylation.

Disease

Known diseases associated with this structure: Leigh syndrome, X-linked OMIM:[300502], Pyruvate dehydrogenase E1-beta deficiency OMIM:[179060], Pyruvate dehydrogenase deficiency OMIM:[300502]

About this Structure

2OZL is a Protein complex structure of sequences from Homo sapiens with MG, K and TPP as ligands. Active as Pyruvate dehydrogenase (acetyl-transferring), with EC number 1.2.4.1 Full crystallographic information is available from OCA.

Reference

Phosphorylation of Serine 264 Impedes Active Site Accessibility in the E1 Component of the Human Pyruvate Dehydrogenase Multienzyme Complex., Seifert F, Ciszak E, Korotchkina L, Golbik R, Spinka M, Dominiak P, Sidhu S, Brauer J, Patel MS, Tittmann K, Biochemistry. 2007 May 29;46(21):6277-6287. Epub 2007 May 3. PMID:17474719

Page seeded by OCA on Mon Nov 12 23:18:36 2007